Stephen Kleene (1909–1994) was an American mathematician and logician, one of the founders of the theory of computation. His surname is tricky — it rhymes with "clay-knee," and he spent much of his life gently correcting people who said "kleen." His mathematics turned out to be the hidden engine behind text search everywhere.
Kleene worked out the deep link between simple pattern-matching machines and the patterns
themselves, giving us the theory of
a* — is literally called the Kleene star in his honour.
Beneath the fearsome logic, Kleene was a warm and playful figure. He was a keen mountain climber and outdoorsman who could tell tall tales for hours, and he served as a Navy officer during the war. Students remembered him laughing his way through the driest material — proof that even the abstract heights of mathematical logic can come with a sense of humour.